Experimental protocols can be divided into four groups; 1) determination of the source of new Dopa-positive melanocytes found in skin after ultraviolet radiation and DMBA treatment, 2) the possible interactions between vitamin D synthesis in the skin and melanogenesis, 3) continuation of the studies on pure cultures of melanocytes with special reference to UV radiation, 4) to study the epidermal melanin unit in vivo and in vitro.